1. Field of the Invention
The present invention pertains to power tools. More particularly, the present invention pertains to power tools which are driven by external drive means.
2. Prior Art
There are a variety of power tools known in the art which are adapted to be powered by external drive means. Commonly, the external drive means comprises a hand held power drill which is particularly suited to this application. The drill or motor may be "chucked" directly onto the pinion gear or input shaft in place of a bit and rotated thereby.
Generally, externalizing drive means is economical and efficient as a single motor is used to power a variety of tool accessories, rather than providing a separate motor for each tool which remains idle when that tool is not used. However, heretofore, the economics inherent in externally powered tools were accompanied by a loss of flexibility and convenience. For example, in known, externally powered tools that gear reduction ratio is fixed and must be used for all purposes. Accordingly, the output speeds of such externally driven tools are not easily adjustable. However, as different types of work require different tool speeds and power output ratios, fixed output ratio, externally driven tools often prove unsuitable for a number of applications.
Accordingly, substantial benefits would be achieved by providing a convenient means for adjusting the output speed of externally driven power tools in accordance with the nature of the work to be performed.